* Acceleration is the rate of change of velocity. Velocity has both speed and direction.

* Acceleration can be in the same direction as the motion, opposite to the motion, or at an angle to the motion.

Here's a breakdown of the different scenarios:

* Acceleration in the same direction as motion: This means the object is speeding up. For example, a car accelerating forward.

* Acceleration opposite to the direction of motion: This means the object is slowing down. For example, a car braking to a stop.

* Acceleration at an angle to the direction of motion: This means the object is changing direction while possibly also changing speed. For example, a ball thrown in a parabolic arc.

Key Point: Acceleration describes how the *velocity* is changing, not just the speed.